no exact number, but less than 5%.

 

I don't know how far I can swim, I've never measured. But I took a swimming test at a summer camp when I was in high school, had to swim a few laps and then tread water for 30 or so minutes. It was hard, but I did it. :dunno: I love to swim, and it's always been natural to me.

 

wow, tread water for 30min
thats longer than playing a water polo game